Abstract
Fossils of the sponge Angulosuspongia sinensis from calcareous mudstones of the middle and upper part of the Kaili Formation (Cambrian Stage 5) in the Jianhe area of Guizhou province, South China, exhibit an apparently reticulate pattern, characteristic of the Vauxiidae. Energy Dispersive X-Ray Spectrometry (EDS) and Raman spectroscopy analysis indicate the presence of silica in the skeletal elements of these fossils, suggesting that this taxon possessed a skeleton comprised of spicules. This is the first confirmation of siliceous skeletal elements in fossils of the family Vauxiidae, and it lends support to the hypothesis that some early demosponges possessed biomineralized siliceous skeletons, which were subsequently lost and replaced by spongin later in the evolutionary history of this lineage. The new materials provide critical insight into the phylogeny and evolution of biomineralization in the Demosopongiae.
Highlights
To date, the best-known early aspiculate poriferans are those assigned to the family Vauxiidae Walcott, 1920, which is known primarily from the Cambrian
For this reason we have studied a new genus and species, Angulosuspongia sinensis[30], a vauxiid sponge from the middle and upper part of the Kaili Formation (Cambrian Series 3, Stage 5) of Jianhe, Guizhou, South China (Fig. 1)
The new material lends support to the hypothesis that some early demosponges possessed biomineralized siliceous skeletons, and later in their evolutionary history, silica was replaced by spongin
Summary
The best-known early aspiculate poriferans are those assigned to the family Vauxiidae Walcott, 1920, which is known primarily from the Cambrian. The skeletal composition of the Vauxidae has been reinterpreted a number of times[21,22,23,24,25,26], but recently, Ehrlich et al.[27] confirmed chitin in the skeleton of Vauxia gracilenta, and concluded that it was a “keratose” demosponge rather than mineralized spicules, and proposed that the Vauxiidae were likely to be the most basal definitive demosponge group known This contrasts with a recent hypothesis that some aspiculate sponge skeletons were derived evolutionarily through demineralization of siliceous spicules and loss of spicules may have happened at least twice in the Demospongiae[20]. The new material lends support to the hypothesis that some early demosponges possessed biomineralized siliceous skeletons, and later in their evolutionary history, silica was replaced by spongin
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